The disclosures herein relate generally to internal combustion engines and more particularly to a rotary engine with stationary adjacent combustion chambers.
Increasing thermal efficiency is a key objective in the design and operation of engines, regardless of the type of engine. It is known that increasing the thermal efficiency of an engine has a direct impact on increasing power output and reducing harmful emissions. Current environmental and fuel supply issues make it necessary and beneficial to continually identify improved engine designs and operating techniques for increasing the thermal efficiency of internal combustion engines.
Internal combustion rotary engines illustrate one example of an energy efficient alternative to a conventional reciprocating piston-type engine. Internal combustion rotary engines are known to provide a relatively high power output for a relatively small physical engine size. Furthermore, due to the rotating operation, rotary engines are capable of operating at high engine speeds relative to typical reciprocating engines. For these reasons, internal combustion rotary engines have been used in several modern day automotive applications and several internal combustion rotary engine designs have been suggested.
U.S. Pat. No. 5,372,107 discloses a rotary engine having an oval rotor that is centrally mounted in a cylindrical chamber. The rotor is mounted on a partially hollow shaft. The cylindrical chamber includes a plurality of sliding vanes spaced around the perimeter of the cylindrical chamber. The sliding vanes are sidably mounted in the cylindrical chamber and seal against the rotor, partitioning the cylindrical chamber to provide a plurality of chambers defined between each adjacent pair of vane seals and a surface of the rotor. Each chamber is subjected to intake compression, and power events.
U.S. Pat. No. 5,247,916 discloses a rotary engine including a housing and a rotor mounted on a shaft in a cylindrical chamber of the housing. The rotor includes an eccentric compression lobe and an eccentric expansion lobe. An air-fuel intake mixture is compressed within a compression chamber defined by the cylindrical chamber, the compression lobe of the rotor and a compression gate after being introduced through an intake manifold. After being compressed, the air-fuel intake mixture is transferred to a rotating combustion chamber, in which combustion of the gases is initiated by an ignition device. After ignition, the compressed air-fuel intake mixture forms expanding combustion gases that are transferred to a space defined by the cylindrical chamber, the expansion lobe of the rotor and an expansion gate, causing rotation of the rotor. The eccentric design of the expansion lobe limits each rotor to only one power event per revolution.
U.S. Pat. Nos. 4,860,704 and 4,741,164 each disclose a rotary internal combustion engine which includes a lobed expansion rotor and a lobed compression rotor mounted on a common engine shaft in a side-by-side configuration. The expansion and compression rotors are mounted in corresponding cylindrical chambers of an engine housing such that an expansion chamber and a compression chamber are defined between corresponding cylindrical chambers and the respective rotor. The engine housing includes a single combustion chamber adjacent to the expansion chamber. During rotation of the rotors, compressed air is developed within the compression chamber and is communicated from the compression chamber to the combustion chamber through a combustor passage. Fuel is added to the compressed air such that a combustible intake mixture is formed. A first hinged valve controls the flow of the compressed air from the compression chamber to the combustion chamber. Ignition of the intake mixture forms a combustion gas that is communicated from the combustion chamber to the expansion chamber through a second hinged valve, such that pressure is exerted against the expansion rotor for forcefully rotating the engine shaft. The ability to increase the thermal efficiency of this engine is significantly limited by the rates at which the intake charge and combustion take place in a single combustion chamber rotary engine. Furthermore, because the second hinged valve rides on lobes of the expansion rotor, the movement of the second hinged valve, and thus the intake and power events, are largely dictated by the lobe profile of the expansion rotor. Accordingly, even though the intake and power events take place in separate physical environments, these two events are not functionally separable.
Internal combustion rotary engines are particularly well suited for independently performing the expansion and combustion phases of the power events and for independently performing the compression and power events. By doing so, to the degree that a specific engine configuration permits, each of these events can be individually designed and controlled such that the thermal efficiency is increased. However, previous attempts to develop an internal combustion rotary engine configuration that allows the various engine events to be separately performed have been costly to implement, provided only marginal improvements in the thermal efficiency and exhibited unacceptable reliability.
Therefore, what is needed is a cost-effective and reliable internal combustion rotary engine that permits the various engine events and phases of the events to be separately performed, and that permits multiple power events per rotor cycle.
Accordingly, in one embodiment, a rotary engine provides a plurality of power events per cycle of the rotor and permits the combustion and expansion phases of the power event to be separately controlled. To this end, a rotary engine includes an expansion rotor housing having a generally cylindrical expansion rotor cavity. An elongated shaft extends through the expansion rotor cavity along a centroidal axis of the expansion rotor housing. A first set of adjacent combustion assemblies is attached to the expansion rotor housing. Each one of the combustion assemblies includes a combustion chamber. An expansion rotor is mounted on the shaft in the expansion rotor cavity such that the elongated shaft extends through a centroidal axis of the expansion rotor.
A principal advantage of this embodiment is that the thermal efficiency is increased, contributing to increased performance and reduced harmful emissions.